Preparation of iron-loaded alginate gel beads and their release characteristics under simulated gastrointestinal conditions

The formulation and processing variables affecting the preparation of iron-loaded alginate beads for potential use as controlled release carriers were studied. The effect of alginates with different mannuronic/guluronic acid ratios, calcium concentration, loading of iron (II) and iron (III) compounds, variable iron loading times and incorporation of iron at different stages in the preparation were considered. Two successful strategies for the incorporation of iron into alginate beads involved using a mixed iron/calcium cross-linking bath or taking preformed calcium cross-linked beads and subsequently loading them with iron. Beads with 50–80 mg iron/g dried bead could be made with ferrous gluconate, high guluronic acid alginate and the mixed cross-linking bath method. Beads with higher loading, up to 180 mg iron/g dried bead, could be made by loading ammonium ferric citrate. Under simulated gastrointestinal conditions the beads progressively released iron in nutritionally relevant amounts.